JPS6036346B2 - Electro gas arc welding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to vertical automatic welding performed using a composite wire for automatic welding. The present invention relates to an electrogas arc hot saddle method that enables beautiful weld beads to be obtained during welding.

Currently, electrogas arc welding is used in the manufacture of ships, cylindrical oil storage tanks, etc. using mild steel, 50kg T steel, 60kg HT steel, etc. from the viewpoint of construction efficiency.

However, in conventional electrogas arc welding, such as the technique described in JP-A-49-115951, it is only stated that it is desirable to have a small amount of slag-forming agent in the wire. No special restrictions were placed on the amount of generator. Using such a compound welding length, 1 weld length is 2. When welding a cylindrical crude oil tank that also serves as a track, there will be too much slag or too little slag produced during welding, making it impossible to obtain a smooth and beautiful bead.

The weld bead is not smooth and beautiful, but has irregularities, and a shape with notches is undesirable because stress concentration will be significant and the fracture strength will be significantly reduced. Therefore, while it is of course necessary to obtain a weld metal with excellent mechanical performance in on-site construction, the first priority is to obtain a smooth and beautiful bead with no internal defects over the entire length of the weld line. Therefore, the development of such a welding method has been strongly desired.

In order to meet the strong demands of the industry, the present inventors conducted a detailed study on the relationship between the filling rate of the slag forming agent in the composite wire and the groove shape, and as a result, the present invention was achieved.

That is, the present invention deals with the ratio S/V of the volume V of the groove, which is an estimated value of the amount of welded metal, and the surface area S of the groove, which is an estimated value of the total bead surface area of the front and back surfaces, or at least one of them, and the composite welding of this. The relationship between the filling rate y of the slag-forming agent in the wire is between the straight line y=≦ and y=2-life in Fig. 3, as shown in the example of the comparison region, when the groove shape or the composite wire is selected. This is an electrogas arc welding method characterized by welding.

The present invention will be explained in detail below.

First, in the present invention, the volume V of the groove is defined as the volume of the weld metal being 1
It means the space deposited in each pass, that is, the estimated value of the amount of deposited metal, and in the case of the groove shape shown in Fig. 1A, (L + G
)

At checkpoints like the entrance in Figure 1, packing passes (B.P.
．． ), Finishing Pass (F.P.) and (L+G>
Xki×KyoXI is the volume V at the time of welding. Next, the surface area S of the groove means the estimated value of the total surface area of the bead for each pass, or at least one of the front and back surfaces, to which slag generated during welding adheres, and is the estimated value of the bead surface area of the joint shape shown in Figure 1 A. In this case, the sum of L×1 and G×1 is S.

In addition, in the case of a checkpoint shape such as the opening in Figure 1, B. P. The groove surface area S during side welding is L×10G×1, and F. P. S at the time of side support is L×1 as described later. In this case, the reason why the groove surface area S is defined as described above is as follows.

In vertical welding using a copper plate abutment, it is essential to generate a thin slag layer between the copper abutment and the bead in order to obtain a beautiful bead surface shape. That is, when an appropriate amount of slag forming agent is supplied, slag is generated just enough to fill the gap between the deposit and the bead, and the desired purpose can be achieved. However, if the amount of slag produced is too large, it cannot be consumed only on the bead surface, and it will cover the entire surface of the molten pool.The slag will be blown away by the arc force, causing slag splashing, and when it is difficult to perform electroslag welding. becomes. Therefore, the slag-forming agent must be supplied from the wire to the extent necessary to improve the bead shape over the entire length of the weld line, that is, to generate enough slag to just cover the bead surface. Therefore, the amount of slug required for each pass is directly related to the bead surface area at that time. That is, a copper abutment is applied to both sides of the groove, and a bead surface is formed on both sides of the groove. P. In side welding, etc., the estimated value of the surface area of the front and back beads is represented by the sum of the areas L x 1 and G x 1 on both sides of the joint, so this value is S. Figure opening F. P. In the case of welding joints such as joints, only one side of the weld where the copper abutment is located becomes the bead surface, and slag adhesion occurs only on this side of the surface. Therefore, the tip surface area S in such a case is L×] as described above. In addition, in vertical welding, even if the plate thickness changes, the joint width on the front and back sides hardly changes, so the peed width remains almost constant, and the slag consumption per unit weld length hardly changes. . Therefore, in the case of a thin plate, since the amount of welded metal is small, the slag consumption is relatively large compared to the amount of welded metal, and the slag forming agent in the wire is released, so a composite wire must be selected. On the other hand, in the case of thick plates, a wire containing a small amount of slag forming agent must be selected and used. Next, the present inventors machined a 50kg HT steel plate with a plate thickness of 6 to 35 ribs into the groove shown in Figure 1A, and determined the volume V of the joint where the deposited metal accumulates even with a welding length of 2h, and the slag produced. We clarified the relationship between the ratio S/V of the bead surface area S, which corresponds to the bead surface area on which the slag-forming agent adheres and solidifies, and the filling rate y of the slag forming agent in the composite wire. In this case, the outer sheath material of the composite wire was made of mild steel, the diameter was on the 1.6 side, and the cross-sectional shape was A in FIG. The alloy composition of the wire is 6
It was adjusted for 0kg HT steel, and the slag forming agent was mainly metal fluoride added in an amount of 0 to 9% by weight relative to the wire. The welding conditions were 310A-32V for the 6-thickness plate, and 450A-42V for the 12.7-thickness side and above. For plate thicknesses of 12.7 ribs or more, the wire is vibrated 120 times/min in the plate thickness direction within the groove to disperse the arc generation points and homogenize the heat input distribution. We aimed to improve the shape of the melt.
In either case, the shielding gas was C02 and flowed at 301/min, and a fixed steel abutment was applied to the back side of the groove, and a sliding steel abutment was applied to the front side, and vertical automatic welding was performed. Looking at Figure 3 showing the experimental results, the ratio S/V of the bead surface area S (ground), which is the estimated value of the total bead surface area of the front and back surfaces or at least one of them, and the volume V (clump), which is the estimated value of the amount of deposited metal. It can be seen that the filling rate y (%) of the slag forming agent in the composite wire required to perform good welding increases in proportion to .

In this case, in the region where y < It was dry. On the other hand, in the region where the relationship y〉2-life exists, the amount of slag generated is greater than the amount of slag consumed on the bead surface, and the molten pool is overflowing with the generated slag, resulting in frequent occurrence of slag saddle 6, which prevents stable welding. I couldn't continue. Therefore, in the present invention, stable welding with no excess or deficiency of slag generation can be achieved when the filling rate of the slag forming agent in the wire is within a range between the filling rate and the life span. It turned out that. Note that the slag forming agent for the composite wire used in the present invention includes CaF2, NaF,
Metal fluorides such as LiF and CeF3 are mainly used, but metal carbonates such as CaC03, C03 and LiC03 and metal oxides such as Ti02, Si02, Mn02 and Zr02 can also be used, and the slag referred to in the present invention The filling rate y of the generating agent is the filling weight ratio (percentage) of these metal fluorides, metal carbonates, and metal oxides to the total weight of the wire.
It is.

By the way, there are no particular restrictions on the application of the present invention, and regardless of the groove shape, the ratio S/V of the groove volume V to the joint surface area S and the slag forming agent in the wire If the filling rate y is in the relationship according to the present invention, it can be widely applied regardless of the distinction between V-groove and x-groove, the presence or absence of a root face, and the size of the wire diameter. However, from the viewpoint of construction efficiency and weld performance, it is better to have the joint to be welded as narrow as possible. For example, it is desirable to have a narrow gap with a root gap of 4 to 7 ribs and a surface gap of about 15 skins. . Furthermore, when welding thick plates with narrow joints, the welding wire is vibrated in the thickness direction of the plate at approximately 30 to 200 times per minute to disperse the heat input by moving the arc point.
It appears that more desirable results can be obtained by perfecting the penetration of both sides of the base material. Applicable steel type is mild steel, 50kgH
It can be applied not only to T steel and 60kg HT steel, but also to low temperature steel, etc. Furthermore, in addition to European steel, low-alloy steel or high-alloy steel can be used as the sheath material of the composite wire used in the present invention, and there are no particular restrictions on the diameter or cross-sectional shape, but it is possible to reduce welding heat input. 2. In order to improve the performance of welded parts, the settling speed is high. It is desirable to use tsumugi flea wire that is smaller than the size of a pig. Composite wire contains iron powder, 0.5-1.5% S
i, 1.0-3.5% Mn and 3% or less Mo, 10
% or less Ni and Cr, 1.5% or less Ti, AI, Zr
, V, or 0.04% or less of B can be appropriately added to improve the mechanical performance of the weld metal. The shielding gas of the welding method according to the present invention is most commonly C02, but mixed gases such as C02-02, Ar-C02, Ar-02, etc. can also be used.

In particular, a mixed gas with Ar is effective in reducing spatter. Next, the effects of the present invention will be explained in more detail using Examples.

Example Table 1 summarizes the results of the Examples.

Table 1 Table 1 (Notes) *In Comparison Table 1, test ship. 1~M. 4 and no. 7~No
．． 9 is the welding method of the present invention, M. 5. Earth. 6 and no. 10 is a comparative example.

A water-cooled fixed steel plate was used on the back side and a water-cooled sliding steel plate was used on the front side as the welding material, and the welding length was 2. It was the axis.

Test No. according to the present invention. In this case, the appropriate amount of slag was generated during welding regardless of the groove shape, the diameter of the composite wire, or the material of the outer sheath, and as a result, the weld bead was completely covered thinly and uniformly, resulting in a smooth and beautiful bead.

On the other hand, test no. In the case of Comparative Example No. 5, too much slag was produced, and slag problems started to occur when the welding length reached 300mm, and at 50mm, the slag completely covered the molten pool, making it impossible to continue welding. Ta.

Also, No. 6 and no. In the case of Comparative Example No. 10, there was insufficient slag, and the slag could not cover the entire surface of the weld bead and only adhered to the surface in spots, which had no effect of improving the bead shape at all, and on the contrary, caused unevenness on the bead surface. Therefore, beads with a beautiful appearance could not be obtained.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the groove shape used in the example, Fig. 2 is a diagram showing an example of the cross-sectional shape of the composite wire used in the present invention, and Fig. 3 is the joint shape and the amount of slag forming agent in the composite wire. FIG. Hair 2 drawings Tano drawings 3 drawings

Claims (1)

[Claims] 1 The ratio S/V of the volume V of the groove, which is the estimated value of the amount of deposited metal, and the surface area S of the groove, which is the estimated value of the total bead surface area of the front and back surfaces, or at least one of them, and the ratio S/V of the groove in the composite wire to be welded. The groove shape or the composite wire should be adjusted so that the relationship with the filling rate y of the slag forming agent is within the region sandwiched between the straight lines y=S/V and y=2.5S/V in FIG. An electrogas arc welding method characterized by selective welding.